﻿/*
 * A JavaScript implementation of the SHA256 hash function.
 *
 * FILE:	sha256.js
 * VERSION:	0.8
 * AUTHOR:	Christoph Bichlmeier <informatik@zombiearena.de>
 *
 * NOTE: This version is not tested thoroughly!
 *
 * Copyright (c) 2003, Christoph Bichlmeier
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holder nor the names of contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * ======================================================================
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ''AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/* SHA256 logical functions */
function rotateRight(n: number, x: number) {
  return (x >>> n) | (x << (32 - n))
}
function choice(x: number, y: number, z: number) {
  return (x & y) ^ (~x & z)
}
function majority(x: number, y: number, z: number) {
  return (x & y) ^ (x & z) ^ (y & z)
}
function sha256_Sigma0(x: any) {
  return rotateRight(2, x) ^ rotateRight(13, x) ^ rotateRight(22, x)
}
function sha256_Sigma1(x: any) {
  return rotateRight(6, x) ^ rotateRight(11, x) ^ rotateRight(25, x)
}
function sha256_sigma0(x: number) {
  return rotateRight(7, x) ^ rotateRight(18, x) ^ (x >>> 3)
}
function sha256_sigma1(x: number) {
  return rotateRight(17, x) ^ rotateRight(19, x) ^ (x >>> 10)
}
function sha256_expand(W: any[], j: number) {
  return (W[j & 0x0f] +=
    sha256_sigma1(W[(j + 14) & 0x0f]) + W[(j + 9) & 0x0f] + sha256_sigma0(W[(j + 1) & 0x0f]))
}

/* Hash constant words K: */
const K256 = [
  0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
  0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
  0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
  0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
  0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
  0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
  0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
  0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
]

let ihash: any[]
let count: any[]
let buffer: any[]
const sha256_hex_digits = '0123456789abcdef'

/* Add 32-bit integers with 16-bit operations (bug in some JS-interpreters:
overflow) */
function safe_add(x: number, y: number) {
  const lsw = (x & 0xffff) + (y & 0xffff)
  const msw = (x >> 16) + (y >> 16) + (lsw >> 16)
  return (msw << 16) | (lsw & 0xffff)
}

/* Initialise the SHA256 computation */
function sha256_init() {
  ihash = new Array(8)
  count = new Array(2)
  buffer = new Array(64)
  count[0] = count[1] = 0
  ihash[0] = 0x6a09e667
  ihash[1] = 0xbb67ae85
  ihash[2] = 0x3c6ef372
  ihash[3] = 0xa54ff53a
  ihash[4] = 0x510e527f
  ihash[5] = 0x9b05688c
  ihash[6] = 0x1f83d9ab
  ihash[7] = 0x5be0cd19
}

/* Transform a 512-bit message block */
function sha256_transform() {
  let a
  let b
  let c
  let d
  let e
  let f
  let g
  let h
  let T1
  let T2
  const W = new Array(16)

  /* Initialize registers with the previous intermediate value */
  a = ihash[0]
  b = ihash[1]
  c = ihash[2]
  d = ihash[3]
  e = ihash[4]
  f = ihash[5]
  g = ihash[6]
  h = ihash[7]

  /* make 32-bit words */
  for (let i = 0; i < 16; i++)
    W[i] =
      buffer[(i << 2) + 3] |
      (buffer[(i << 2) + 2] << 8) |
      (buffer[(i << 2) + 1] << 16) |
      (buffer[i << 2] << 24)

  for (let j = 0; j < 64; j++) {
    T1 = h + sha256_Sigma1(e) + choice(e, f, g) + K256[j]
    if (j < 16) T1 += W[j]
    else T1 += sha256_expand(W, j)
    T2 = sha256_Sigma0(a) + majority(a, b, c)
    h = g
    g = f
    f = e
    e = safe_add(d, T1)
    d = c
    c = b
    b = a
    a = safe_add(T1, T2)
  }

  /* Compute the current intermediate hash value */
  ihash[0] += a
  ihash[1] += b
  ihash[2] += c
  ihash[3] += d
  ihash[4] += e
  ihash[5] += f
  ihash[6] += g
  ihash[7] += h
}

/* Read the next chunk of data and update the SHA256 computation */
function sha256_update(data: string, inputLen: number) {
  let i
  let index
  let curpos = 0
  /* Compute number of bytes mod 64 */
  index = (count[0] >> 3) & 0x3f
  const remainder = inputLen & 0x3f

  /* Update number of bits */
  if ((count[0] += inputLen << 3) < inputLen << 3) count[1]++
  count[1] += inputLen >> 29

  /* Transform as many times as possible */
  for (i = 0; i + 63 < inputLen; i += 64) {
    for (let j = index; j < 64; j++) buffer[j] = data.charCodeAt(curpos++)
    sha256_transform()
    index = 0
  }

  /* Buffer remaining input */
  for (let j = 0; j < remainder; j++) buffer[j] = data.charCodeAt(curpos++)
}

/* Finish the computation by operations such as padding */
function sha256_final() {
  let index = (count[0] >> 3) & 0x3f
  buffer[index++] = 0x80
  if (index <= 56) {
    for (let i = index; i < 56; i++) buffer[i] = 0
  } else {
    for (let i = index; i < 64; i++) buffer[i] = 0
    sha256_transform()
    for (let i = 0; i < 56; i++) buffer[i] = 0
  }
  buffer[56] = (count[1] >>> 24) & 0xff
  buffer[57] = (count[1] >>> 16) & 0xff
  buffer[58] = (count[1] >>> 8) & 0xff
  buffer[59] = count[1] & 0xff
  buffer[60] = (count[0] >>> 24) & 0xff
  buffer[61] = (count[0] >>> 16) & 0xff
  buffer[62] = (count[0] >>> 8) & 0xff
  buffer[63] = count[0] & 0xff
  sha256_transform()
}

/* Split the internal hash values into an array of bytes */
// eslint-disable-next-line @typescript-eslint/no-unused-vars
// function sha256_encode_bytes() {
//   let j = 0
//   const output = new Array(32)
//   for (let i = 0; i < 8; i++) {
//     output[j++] = (ihash[i] >>> 24) & 0xff
//     output[j++] = (ihash[i] >>> 16) & 0xff
//     output[j++] = (ihash[i] >>> 8) & 0xff
//     output[j++] = ihash[i] & 0xff
//   }
//   return output
// }

/* Get the internal hash as a hex string */
function sha256_encode_hex() {
  let output = new String()
  for (let i = 0; i < 8; i++) {
    for (let j = 28; j >= 0; j -= 4) output += sha256_hex_digits.charAt((ihash[i] >>> j) & 0x0f)
  }
  return output
}

/* Main function: returns a hex string representing the SHA256 value of the
given data */
function digest(data: string) {
  sha256_init()
  sha256_update(data, data.length)
  sha256_final()
  return sha256_encode_hex()
}

export default digest
